and plug in the one on the port back up alternator. If that one goes TU I replace the one on the starboard alternator with one out of my spare parts and return to running with my primary alternator . If that one goes TU I replace it with my second spare. By that time I should have figured out what is causing me to burn up the last two or three $350.00 dollar regulators. Either that or I'm really stupid. If I ever have to get down to using a light bulb I'm in serious trouble. Spare parts, always carry spare parts! And lots of them! Spare part are your friends.